The present invention refers to an implant for the operative correction of spinal deformity, such as scoliosis, kyphosis, and lordosis from the rear access.
Since 1962 the HARRINGTON distraction rod is known, comprising at its upper end a multitude of saw notches which are able to receive a hook and which are formed thus that a force between the hook and the rod can only be applied in one direction, in the direction of distraction. At the lower end of the rod there is a collar serving as stop for a fixed hook. For correcting a spinal deformity two hooks are arranged at the distraction rod, on both sides of the deformity, whereby the lower hook is fixed and the upper hook is displaced thus that the desired correction of the deformity of the spine is effectuated.
Since 1961 the HARRINGTON compression rod is also known. It comprises a thread along its entire length for receiving nuts. With the aid of the nuts hooks, running by a bore on the rod, can be displaced. They are fastened on the convex side of the deformity. They are displaced against each other, thus shortening the convex side, resulting in a supplemental correction of the deformity.
The two HARRINGTON rods form a system exercising distraction and compression forces for the correction of a spinal deformity from the rear.
A correction implant for the ventral derotation spondylodese (known as V.D.S.) is further known, consisting of a compression rod with thread, on which nuts are displaceable. Those nuts fit with a cylindrical part in a recess in bone screws. By displacing the bone screws on the threaded rod the convexity of a deformity can be reduced. This V.D.S. system is predominantly suited for the ventral access. If it is employed dorsal transpedicular, that is through the arch root, it must be used bilateral, that is on both sides of the spine.